328 CALIFORNIA ACADEMY OF SCIENCES. [Proc. 3D Ser. 



some of the fibers is broken by the septum which separates 

 calyx and stalk, but a large number of them pass through 

 the septum without interruption. 



The somatic portion of the ventral muscle and its direct 

 continuation into the stalk are shown in fig. 3. This rep- 

 resents a para-sagittal section near the median plane. The 

 space between the ventral body-wall {y. zt>.) and the oesoph- 

 agus {ces.) is seen to be completely filled with longitudinal 

 muscle fibers. At the focus which is here represented, many 

 of these fibers are seen to pass over the septum into the stalk. 

 At a deeper focus, the septum comes into view, bounded 

 on each side by .the large nuclei {mi.) which mark the 

 attachment of those muscle fibers which are not continuous. 

 At the base of the sphincter muscle {sph. loph.) the fibers 

 are seen to unite with the ectoderm. In cross-sections of 

 the calyx in this region, the intermingling of the longitudi- 

 nal muscle fibers with those of the sphincter may be clearly 

 seen. There can not, however, be said to be any direct 

 union between the muscles of these two systems, although 

 their union of action seems probable. Figure 4 is a frontal 

 section close to the ventral wall of the stomach. Here the 

 direct passage of a number of the muscle fibers {v. m.f.) 

 from stalk to calyx is clear and undoubted. At each side 

 the septum {sef.) is clearly seen through the continuous 

 fibers, while in the middle there is a region where at the 

 focus represented no septum is present. This section shows 

 another interesting fact about the ventral muscle. When 

 the fibers enter the calyx, some of them are seen to diverge 

 right and left. These diverging fibers form branches of 

 the somatic ventral muscle {br. s. v. mus.) which pass on 

 each side of the oesophagus. The empty space in the cen- 

 ter represents the position of the stomach at the base of the 

 oesophagus. In a series of sagittal sections the branching 

 is very evident, and furthermore, it is clear that part, at 

 least, of these diverging fibers attach themselves to the floor 

 of the atrium. In cross-section this is perhaps more evi- 

 dent. Figure 5 represents a cross-section of the stomach 

 and base of the oesophagus. The somatic muscle fibers 



